1. Field of Invention
The present invention relates to the reception and processing of broadcast signals and other electronic signals. More particularly, the present invention provides a means of processing and selecting at least one desired signal from a larger captured band of signals, and may include concurrent processing of multiple signals within the larger captured band of signals.
2. Description of Prior Art
Broadcast signals include a wide array of informational transmissions, which may be distributed either over the air or through cable or other media requiring a physical connection. One illustrative example of such an informational transmission which is available through either an over the air transmission or cable transmissions is television. Traditionally, televisions use a hardwired tuner or other such circuitry to isolate a single frequency within a larger frequency band. These hardwired tuners isolate and amplify one broadcast signal at a time. When a person is watching TV and desires to change the station, the person manipulates the control settings—e.g., the channel knob or remote control channel button—to change the physical characteristics of an oscillator and filter which is typically part of the hardwired tuner within the device. If the TV is equipped with only a single hardwired tuner, it cannot play more than one channel simultaneously. Consequently, in order for a conventional device to simultaneously process or display more than one broadcast signal, the conventional device must have more than one tuner. That is, conventional devices require one tuner, or separate tuner hardware, for each simultaneously displayed station. For example, a typical picture-in-picture television needs at least two tuners, one for the main picture and one for the picture-in-picture display.
FIG. 1 depicts a conventional hardwired television tuner. A radio frequency (RF) signal band 101 is input to a tunable 6 MHz filter 103. The filter 103 removes all but the 6 MHz signal band assigned to a television station. The tunable filter 103 is controlled by a channel selection apparatus 102 which also controls the operation of an oscillator 104. The resulting oscillator signal and filter signal are sent to a mixer 105. From the mixer emerges a 6 MHz wide signal band which corresponds to the selected channel. This signal is traditionally used to drive a television's video and audio functions.
Continuing with the prior illustrative example of television, broadcast signals are available in both analog and digital formats. As used throughout this disclosure, “analog signal”, “analog format”, “digital signal”, and “digital format” are used as shorthand to differentiate different categories of modulation and demodulation techniques. As will be readily understood by those skilled in the art either an “analog signal (format)”or a “digital signal (format)” have analog characteristics, such as rise and fall times for the transmitted signal envelope, upper and lower frequency bounds, and amplitudes (magnitudes) of the transmitted envelope. A traditional analog transmission format, such as frequency modulation (FM) can also be expressed in terms of a digital transmission format of phase modulation.
An “analog signal” may also be viewed as providing baseband information modulated onto a radio frequency using an analog modulation technique. During processing of the received signal, demodulation of the analog modulated baseband signal may be performed either through traditional analog demodulation techniques or through “digitizing” the information utilizing conventional analog-to-digital conversion techniques.
Further, multiple informational transmissions and multiple modulation techniques may be used within a common signal space. The prior illustrative example of television demonstrates one such occurrence of multiple modulation techniques within a common signal space. Using television channel 2, to further refine the example, the following television example provides the following informational transmissions. The overall channel is positioned between 54 and 60 MHz, with a video carrier at 55.25 MHz, a color carrier at 58.83 MHz, and a sound carrier at 59.75 MHz. The composite picture and synchronization signals are amplitude modulated, while the audio is frequency modulated. As will be readily appreciated, if only the audio signal associated with channel 2 is of interest to the user, that signal can be utilized and processed at 59.75 MHz (+/−1000 Hz) independent of the video signal. Similarly, the video signal alone may be utilized without need of processing the audio signal. While in this example the different modulation techniques are separated in frequency, although within the same “channel”, a variety of orthogonal signaling techniques may be used to separate information on a common frequency. Illustrative examples of orthogonal signaling techniques include Code Division Multiple Access (CDMA), Direct Sequence Spreading (DSS), and Cyclic Code Shift Keying (CCSK) systems.